Ultraprecision CMP for sapphire, GaN, and SiC for advanced optoelectronics materials

Investigation on the surface characterization of Ga-faced GaN after chemical-mechanical polishing

“…Hideo Aida et al [12] obtained a low MRR of 17 nm/h and realized an atomically flat surface with Ra = 0.1 nm after 150 h CMP of GaN using slurry with colloidal silica abrasive. Hideo Aida et al [13] also proved that CMP of GaN is shown to obey Prestonian behavior, and presented that the MRR of Ga 2 O 3 is two orders of magnitude higher than that of GaN. Drew Hanser [14] reported surface preparation of substrates from bulk GaN crystals.…”

Extended study of the atomic step-terrace structure on hexagonal SiC (0001) by chemical-mechanical planarization

“…According to the section AFM images, refer to previous results [3], we establish a model to describe the fluctuation surface curve of 4H-SiC as shown in Fig. 6.…”

“…Based on the theory of crystallography and the research development of the hexagonal super-hard materials, such as gallium nitride (GaN), sapphire, 4H-and 6H-SiC [13][14][15][16][17][18], we know that all these materials have an obvious characteristics: if the (0 0 0 1) surface of wafer is approximately 0 • -off, the surface could emerge with atomic step-terrace structure after planarization [3,[19][20][21]. Strictly, for such hexagonal super-hard materials, besides the method of measuring the surface roughness parameter (Ra) of the wafer after planarization by surface measuring instrument, the formation surface atomic step-terrace structure is more persuasive and credible to verify the efficiency of the planarization technique, because the surface atomic step-terrace structure directly show the crystalline form of the surface.…”

“…Defects on the substrate surface could be replicated into the epilayer, thus surface preparation of the substrate wafer will play a critical role in electronic integration fabrication [5]. Due to the extreme hardness and strong stability against chemicals of SiC [6,7], it is more difficult to realize ideal planarization with high removal rate and good surface quality [3]. Chemical mechanical polishing (CMP) is applied to the surface as an efficient treatment to produce atomic level surface flatness by removing the irregularities and the damage on or near the surface due to mechanical polishing [8,9].…”

“…Hexagonal silicon carbide materials (SiC), which are considered to be a promising candidate for electronic devices have recently attracted much attention as the third generation key materials for transistors because they can be operated in high-power, highfrequency regions that are currently inaccessible with conventional silicon-based transistor devices [1][2][3][4]. In most cases, the c-plane (0 0 0 1) of hexagonal SiC substrates is used for device epitaxy.…”